154 



NATURAL HISTORY OF VERMONT 



Part I. 



FRESH YV'ATF.K AND LAND SHELLS. 



last whorl, and greater convexity of the 

 whorls ; from L. iiohi?.trif. of Europe chiefly 

 in the greater convexity of the whorls 

 and less acuiiiination of the spire. By 

 some it is regarded as a variety of the 

 latter. 



Limncca dcsidiosa. — Sat. 

 Description. — Shell brown horn col- 

 or, elongate-ovate ; whorls nearly six, 

 slightly convex ; suture distinct ; spire 

 about as long as the aperture, which is 

 lengthened below ; columellar fold fi^eble ; 

 labi'iim appressed : columella produced be- 

 low the fold in a straight line. Length 

 0.55 inch ; breadth 0.25 inch ; divergence 

 of the spire 45° to 55". 



Remarks. — This species is very com- 

 mon, and is subject to great variation of 

 form, frequently being elongated, and re- 

 sembling L. chiles. Other individuals are 

 short, as in Say's figure (Am. Conch.,) 

 and the upper part of the last whorl is in- 

 flated and more or less shouldered, while 

 the lower part is produced as is usual. 

 This variety approaches L. iiinhilicata of 

 Mass., which has the umbilicus larger, 

 and the lower part of the last whorl ab- 

 breviated, inflated, and globular. 

 Limnaa caperata. — Say. 

 Description.— Shell ovate, brown, with 

 minute revolving raised lines, which are 

 in some very distinct, and in others most- 

 ly obsolete ; whorls nearly six, convex ; 

 suture distinct ; spire about as long as the 

 aperture, conic, acute ; columella reddish, 

 slightly folded, thickened, and reflected 

 over an umbilicus. Length 0.45 inch ; 

 breadth 0.24 inch ; divergence of tiie 

 spire 57°. 



Remarks. — This species is well char- 

 acterized by the revolving raised lines, 

 which will generally be seen around the 

 umbilical region, when obsolete elsewhere. 

 The last whorl and the aperture are more 

 regularly rounded than in the preceding 



species. • 



Genus Fhysa. 

 Goieric Characters. — Sliell heierostrophe, shi- 

 niii", otherwise like Lirnna3a ; operculum want- 

 in" ; animal with long, slender tenlicles ; having 

 the eyes at their base on the inner side. 

 P/tijsa nncUlaria. — Sav. 

 Description. — Shell ovate, yellowish 

 brown, sometimes of a bay color ; whorls 

 four, flattened ; suture not impressed ; 

 spire less than one-fifth of the length of 

 the aperture ; apex acute ; last whorl very 

 large ; aperture acute and narrow above, 

 wide below ; outer lip often thickened 

 within ; columella produced in a right 

 line below its fold. Length 65 inch ; 

 breadth 0.48 inch ; divergence of the 

 scire 110". 



—This species, seldom found 

 is not uncommon in lake 

 It is there found of a deep 



Remarks. 

 plentifully, 

 Ciiainplain. 

 bay color. 



PInjsa hetcrostrojiha. — Say. 



Description. — Shell ovate, brown; 

 whorls five, slightly convex; suture slight- 

 ly impressed ; apex acute ; aperture acute 

 and somewhat narrowed above ; columel- 

 la produced in a right line ; outer lip of- 

 ten thickened within. Length 0.75 inch; 

 breadth 0.45 inch ; divergence of the 

 spire varying in different shells from 65" 

 to 70". 



Rem.\rks. — This species is abundant in 

 various parts of this state. Its young are 

 not easily distinguished from those of the 

 preceding species. 



Phijsa gijrina. — Sat. 



Description. — Shell long-ovate, yel- 

 lowish brown ; whorls five, slightly con- 

 vex ; suture moderately impressed ; apex 

 acute ; aperture less acute above than 

 the preceding species ; columella a little 

 curved below ; outer lip often thickened 

 within. Length 0.55 inch ; breadth 0.75 

 inch; divergence of the spire 50°. 



Remaiik. — This species is very rare in 

 this state. 



Physa Jiypnorum. — Drap. 



Description. — Shell elongate, yellow- 

 ish brown ; whorls si.x, moderately con- 

 vex ; suture well impressed ; apex acute; 

 spire nearly as long as the aperture, 

 which is regularly narrowed to the tip ; 

 columella oblique, in its lower part turned 

 backwards and upwards; outer lip not, 

 thickened within. Length 0.58 inch ; 

 breadth 0.25 inch ; divergence of the 

 spire 45''. 



Remarks. — This species, described by 

 Say as P. cloiiirata, does not differ from 

 the European shell, whose name we have 

 prefixed to it. It is found in swamps and 

 in small sluggish streams. 



The above four species of Physa differ 

 chiefly in the ratio of the spire to the aper- 

 ture, and in the divergence of the former, 

 which de])Piids on the ratio of the length 

 and breadth so far as it is uniform in dif- 

 ferent parts of the spire. The gradation 

 in these characters is parallel, as may be 

 seen by a comparison of their measure- 

 ments. 



Genus Planorbis. 

 Generic Characters. — Shell with the revo- 



